intro:Long ago, the legendary Avatar kept the world and its four nations at peace with each other. However, the Avatar disappeared one hundred years ago, and hasn't been seen since. During that time, the tyrannical Fire Nation used the opportunity to wage war with the other three nations, seeking to conquer them. People began to lose hope that the Avatar would ever return and bring peace back to the world. Even the Southern Water Tribe, located in the distant south pole sea, has been affected by the Fire Nation's war. The men of the tribe all sailed abroad to fight, leaving behind the women and children. Sokka and his younger sister Katara are the oldest of the tribe's children in the south pole.
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Two siblings, Katara and Sokka, are out fishing in a small canoe. Katara, a Waterbender, practices Waterbending, as Sokka prepares to spear a fish. Katara bends the water around a fish to lift it above the canoe; Sokka penetrates the water with the back of his spear, causing the fish to fall back into the water and wetting him. Sokka gets angry and scolds Katara, saying that if he had "wierd powers" he would have kept his wierdness to himself. The sea currents pick up speed, Sokka tries to steer the boat to avoid being collided with the small chunks of floating ice, while Katara gives directions but eventually the boat is crushed between two icebergs, leaving Sokka and Katara stranded in the middle of the sea on a floating chunk of ice. Sokka blames Katara for the mess, which causes her to lose her temper and scold Sokka. As Katara rages, she ends up violently Waterbending without realizing it; soon, she cracks and shatters an iceberg, revealing a giant glowing orb of ice. Seeing the form of a person inside the ice, Katara thinks the person needs help, and begins chopping away at it with Sokka's club, while Sokka warns her not to as they don't know who the person is. The ice breaks, and releases a bright column of light into the sky.
Prince Zuko, a Fire Nation teenager who has been hunting the Avatar for two years, sees the bright light from his ship. With him is his Uncle Iroh. Zuko orders his crew to head toward the light, insisting that the light came from the Avatar.
After Katara breaks through the ice, she finds the person is a young boy with strange arrow-like marks on his head and hands. Sokka is skeptical, and points his spear at the boy. The boy falls out and into Katara's arms. She lays him down and tries to help him. Sokka pokes the boy in the head with the blunt side of his spear, still skeptical, but Katara shoos him away.
The mysterious boy drowsily opens his eyes to see Katara staring at him with deep blue eyes. He quickly becomes fully alert, cheerfully asking Katara if she wants to go Penguin Sledding with him. The boy introduces himself as Aang and sneezes, sending him high into the air, but he slowly drifts back down again unharmed. Katara realizes that he must be an Airbender. Aang climbs back into the ice to find Appa, a very large flying-bison. It takes a moment for Aang to wake him up. Sokka does not believe that the bison could actually fly and walks away but realizes that he is stranded in the middle of the sea and can't go back home. Aang offers them to fly them back to the Southern Water Tribe where they live at which Katara happily agrees while Sokka refuses at first but agrees later as he had no choice.Then the group gets on Appa's saddle. Sokka still refused to believe that Appa could fly. Aang cries "Yip-Yip!", causing Appa to leap into the air, but he comes crashing right back down into the water and starts swimming. Aang figures Appa's still too tired to fly just yet. Aang turns around and stares at Katara with a huge smile on his face, causing her to ask, "Why are you smiling at me like that?", to which he replies "Oh, I was smiling?". After sometime, Katara tells Aang that the last Avatar was supposed to be an Air Nomad, and asks if Aang knew him. Aang awkwardly states that he knew people that knew the Avatar, but did not know the actual Avatar himself.
Later, Aang has a dream about a storm that he and Appa had encountered while they were near the South Pole. He re-lives in the dream how he and Appa were brought under the waves by the intense wind and rain, and how Aang started glowing and created the orb of ice that surrounded him. He is jolted awake, finding himself in a tent in the Southern Water Tribe and being awakened by Katara. He quickly gets dressed, with Katara watching. She notices the arrow markings running along his body, and then when he's completely dressed, pulls him into the village to introduce him to the entire village which was quite small.
Everyone acts surprised to see an Airbender, as no one has seen an Air Nomad in a hundred years, thinking they must have become extinct. Sokka wonders why Aang always carries a staff around, realizing it's not sharp enough to stab anybody, and Aang shows them how he uses Airbending to fly with it. Aang ends up accidentally crashing into Sokka's poorly-constructed watch tower. Kanna (aka Gran Gran), the grandmother of Katara and Sokka, is wondering if Aang may be a threat to the tribe. Katara wants him to stay, believing he could teach the village so many good things and also teach her waterbending. They happen to glance over at Aang, who is showing off to the village toddlers how he can stick his tongue to his staff.
On the Fire Nation ship, Prince Zuko is practicing his Firebending techniques, with Uncle Iroh as his mentor. Zuko becomes impatient and asks for his uncle to teach him advanced moves, but Iroh demands he master the basics. But finally he agrees.
Sokka begins to teach the young boys, lecturing them about how they are the warriors of this tribe, until one of them says innocently they need to pee. Sokka gets mad at Aang for distracting his "warriors" with fun and games and throws a fit. When Aang sees a penguin, he gets excited and tries to capture it, but it's too fast and slippery. Katara approaches and agrees to teach him the "fine art" of catching penguins, in exchange for lessons in Waterbending. However, Aang points out that he knows nothing about Waterbending, being an Airbender, and tells her that she could learn from the other people in the tribe but Katara tells him that she is the only waterbender in the whole South Pole. Aang says that the Nothern Water Tribe should have waterbenders to teach Katara and offers her to fly her to the North Pole. Katara was not sure to leave her tribe and then Aang suggests to her that she could think about it later and in the meantime she could teach him to catch penguins and so Katara begins her lessons.
Aang and Katara go penguin sledding, having fun until they accidentally slide near an old abandoned Fire Navy ship. Aang wants to go in and explore it, but Katara is wary. She has been told never to go onto the Fire Navy ship, but Aang convinces her. As they explore the ship, Aang wonders why a Fire Nation ship was so far from its home. Katara realizes Aang has no knowledge of the war at all, as she learns that he was trapped in the iceberg for one hundred years. They accidentally set off a booby trap in the ship, sending off a flare into the sky. Aang saves Katara by Airbending out of the ship. But Prince Zuko has seen the flare and Aang escaping from the ship, and Zuko believes he has found the long lost Avatar at last.
